[gnome-remote-desktop] vnc: Copy pixels using the right destination stride

[Jonas Ådahl <jadahl src gnome org>]

commit 4d358762948dccdcac6d01f4dd7b8635e53de979
Author: Jonas Ådahl <jadahl gmail com>
Date:   Mon Oct 12 17:34:30 2020 +0200

    vnc: Copy pixels using the right destination stride
    
    We're copying the pixels in a separate thread managed by PipeWire, and
    in this thread, accessing the VNC framebuffer dimension and stride is
    racy. Instead of fetching the dimension directly, pass the expected
    width and get the stride it will eventually have.
    
    Already before this patch, when the copied pixel end up on the main
    thread and the dimension still doesn't match up, the frame will be
    dropped.

 src/grd-session-vnc.c         | 5 +++--
 src/grd-session-vnc.h         | 3 ++-
 src/grd-vnc-pipewire-stream.c | 5 +++--
 3 files changed, 8 insertions(+), 5 deletions(-)
---
diff --git a/src/grd-session-vnc.c b/src/grd-session-vnc.c
index a06d34d..ba3e5ce 100644
--- a/src/grd-session-vnc.c
+++ b/src/grd-session-vnc.c
@@ -519,9 +519,10 @@ check_rfb_password (rfbClientPtr  rfb_client,
 }
 
 int
-grd_session_vnc_get_framebuffer_stride (GrdSessionVnc *session_vnc)
+grd_session_vnc_get_stride_for_width (GrdSessionVnc *session_vnc,
+                                      int            width)
 {
-  return session_vnc->rfb_screen->paddedWidthInBytes;
+  return width * BGRX_BYTES_PER_PIXEL;
 }
 
 static void
diff --git a/src/grd-session-vnc.h b/src/grd-session-vnc.h
index 07678c8..ee1f986 100644
--- a/src/grd-session-vnc.h
+++ b/src/grd-session-vnc.h
@@ -55,7 +55,8 @@ void grd_session_vnc_move_cursor (GrdSessionVnc *session_vnc,
                                   int            x,
                                   int            y);
 
-int grd_session_vnc_get_framebuffer_stride (GrdSessionVnc *session_vnc);
+int grd_session_vnc_get_stride_for_width (GrdSessionVnc *session_vnc,
+                                          int            width);
 
 gboolean grd_session_vnc_is_client_gone (GrdSessionVnc *session_vnc);
 
diff --git a/src/grd-vnc-pipewire-stream.c b/src/grd-vnc-pipewire-stream.c
index 96dd7c9..82ceb9b 100644
--- a/src/grd-vnc-pipewire-stream.c
+++ b/src/grd-vnc-pipewire-stream.c
@@ -326,10 +326,11 @@ process_buffer (GrdVncPipeWireStream *stream,
       int height;
       int y;
 
-      src_stride = buffer->datas[0].chunk->stride;
-      dst_stride = grd_session_vnc_get_framebuffer_stride (stream->session);
       height = stream->spa_format.size.height;
       width = stream->spa_format.size.width;
+      src_stride = buffer->datas[0].chunk->stride;
+      dst_stride = grd_session_vnc_get_stride_for_width (stream->session,
+                                                         width);
 
       frame->data = g_malloc (height * dst_stride);
       for (y = 0; y < height; y++)